How do I maintain the road's texture after applying the curve modifier to make the road a single object?
You have used object coordinates for the texture placement. You want to use UV, in the texture properties window make sure you are using UV for mapping. Before applying the modifiers go into edit mode and hit U->Reset. If this doesn't map the faces correctly to the texture, open image editor screen along the 3d view and adjust the UVs, most likely you just need to rotate by 90 degrees.